[PATCH linux v2] mtd: spi-nor: aspeed-smc: Use io string accessors to fifo

[OpenBMC Patches]

From: "Milton D. Miller II" <miltonm at us.ibm.com>

Make and use new routines to access the fifo when in user mode.
Instead of using memcpy_fromio, base the new routines on the io
port string accessors.

When the smc controllers are configured to transfer in user mode,
the exact address within the chip select region is ignored and
all valid data bytes are sent to the device fifo.  It has been
determined the reason _memcpy_fromio, an arm specific byte-by-byte
variant of memcpy_fromio was required in read_reg, is that the
later will stutter when coping from memory, discarding some
bytes read, when switching from words to bytes for the final
unaligned length.

This change includes a hack to make inw/outw work.  The default
generic IO_SPACE_LIMIT is 0, and twenty bits when PCI is selected.
While there is a PCMCIA SOC config to select the full 4GB space it
would bring in the PCMCIA core for no use to the ast2400.  We want
to be part of the generic multi-platform arm kernel and therefore
mach/io.h is not going to work.  However, the limit is under an
ifndef, so define it in this file an check it was not redefine
at probe time.  To avoid redefinition errors or warnings, guard
the setting with CONFIG_ARM for cross-arch compile testing and
with a Kconfig dependency for arm cross-compile tests.  While some
other architecture may not accept unsigned long addresses as ioport
cookies, that can be addressed when, if ever, the hardware appears
on another arch.

While the change to use the designed-for-memory optimised copy
template, even reusing the bytes of memcpy, was a recent change
and only for little endian arm, designing and proposing a patch
will take some time and there could be debate if the routine
needs to work on changing memory.

Signed-off-by: Milton Miller <miltonm at us.ibm.com>
---
 drivers/mtd/spi-nor/Kconfig      |   2 +
 drivers/mtd/spi-nor/aspeed-smc.c | 120 ++++++++++++++++++++++++++++++++++++---
 2 files changed, 113 insertions(+), 9 deletions(-)

diff --git a/drivers/mtd/spi-nor/Kconfig b/drivers/mtd/spi-nor/Kconfig
index c7554d8..4a963c4 100644
--- a/drivers/mtd/spi-nor/Kconfig
+++ b/drivers/mtd/spi-nor/Kconfig
@@ -44,6 +44,8 @@ config ASPEED_FLASH_SPI
 	tristate "Aspeed flash controllers in SPI mode"
 	depends on HAS_IOMEM && OF
 	depends on ARCH_ASPEED || COMPILE_TEST
+	# IO_SPACE_LIMIT must be equivalent to (~0UL)
+	depends on !NEED_MACH_IO_H
 	help
 	  This enables support for the New Static Memory Controller (FMC)
 	  in the AST2400 when attached to SPI nor chips, and support for
diff --git a/drivers/mtd/spi-nor/aspeed-smc.c b/drivers/mtd/spi-nor/aspeed-smc.c
index 9dd4609..af8df0a 100644
--- a/drivers/mtd/spi-nor/aspeed-smc.c
+++ b/drivers/mtd/spi-nor/aspeed-smc.c
@@ -8,6 +8,12 @@
  *
  */
 
+/* See comment by aspeed_smc_from_fifo */
+#ifdef CONFIG_ARM
+#define IO_SPACE_LIMIT (~0UL)
+#endif
+
+#include <linux/bug.h>
 #include <linux/device.h>
 #include <linux/io.h>
 #include <linux/module.h>
@@ -19,6 +25,94 @@
 #include <linux/of_platform.h>
 #include <linux/sysfs.h>
 
+/*
+ * On the arm architecture, as of Linux version 4.3, memcpy_fromio
+ * stutters discarding some of the bytes read if the destination is
+ * unaligned, so we can't use it for reading from a fifo to a buffer
+ * of unknown alignment.  Instead use the ins (l, w, b) family
+ * to read from the fifo.   However, ARM tries to hide io port
+ * accesses from drivers unless there is a PCMCIA or PCI device, so
+ * we define the limit before all include files.  There is a
+ * check in probe to make sure this will work, as long as the
+ * architecture uses an identity iomap.
+ */
+
+static void aspeed_smc_from_fifo(void *buf, const void __iomem *iop, size_t len)
+{
+	unsigned long io = (__force unsigned long)iop;
+
+	if (!len)
+		return;
+
+	/* Expect a 4 byte input port.  Otherwise just read bytes */
+	if (unlikely(io & 3)) {
+		insb(io, buf, len);
+		return;
+	}
+
+	/* Align target to word: first byte then half word */
+	if ((unsigned long)buf & 1) {
+		*(u8 *)buf = inb(io);
+		buf++;
+		len--;
+	}
+	if (((unsigned long)buf & 2) && (len >= 2)) {
+		*(u16 *)buf = inw(io);
+		buf += 2;
+		len -= 2;
+	}
+	/* Transfer words, then remaining halfword and remaining byte */
+	if (len >= 4) {
+		insl(io, buf, len >> 2);
+		buf += len & ~3;
+	}
+	if (len & 2) {
+		*(u16 *)buf = inw(io);
+		buf += 2;
+	}
+	if (len & 1) {
+		*(u8 *)buf = inb(io);
+	}
+}
+
+static void aspeed_smc_to_fifo(void __iomem *iop, const void *buf, size_t len)
+{
+	unsigned long io = (__force unsigned long)iop;
+
+	if (!len)
+		return;
+
+	/* Expect a 4 byte output port.  Otherwise just write bytes */
+	if (io & 3) {
+		outsb(io, buf, len);
+		return;
+	}
+
+	/* Align target to word: first byte then half word */
+	if ((unsigned long)buf & 1) {
+		outb(*(u8 *)buf, io);
+		buf++;
+		len--;
+	}
+	if (((unsigned long)buf & 2) && (len >= 2)) {
+		outw(*(u16 *)buf, io);
+		buf += 2;
+		len -= 2;
+	}
+	/* Transfer words, then remaining halfword and remaining byte */
+	if (len >= 4) {
+		outsl(io, buf, len >> 2);
+		buf += len & ~(size_t)3;
+	}
+	if (len & 2) {
+		outw(*(u16 *)buf, io);
+		buf += 2;
+	}
+	if (len & 1) {
+		outb(*(u8 *)buf, io);
+	}
+}
+
 enum smc_flash_type {
 	smc_type_nor = 0,	/* controller connected to nor flash */
 	smc_type_nand = 1,	/* controller connected to nand flash */
@@ -165,8 +259,8 @@ static int aspeed_smc_read_reg(struct spi_nor *nor, u8 opcode, u8 *buf, int len)
 	struct aspeed_smc_chip *chip = nor->priv;
 
 	aspeed_smc_start_user(nor);
-	writeb(opcode, chip->base);
-	_memcpy_fromio(buf, chip->base, len);
+	aspeed_smc_to_fifo(chip->base, &opcode, 1);
+	aspeed_smc_from_fifo(buf, chip->base, len);
 	aspeed_smc_stop_user(nor);
 
 	return 0;
@@ -178,8 +272,8 @@ static int aspeed_smc_write_reg(struct spi_nor *nor, u8 opcode, u8 *buf,
 	struct aspeed_smc_chip *chip = nor->priv;
 
 	aspeed_smc_start_user(nor);
-	writeb(opcode, chip->base);
-	_memcpy_toio(chip->base, buf, len);
+	aspeed_smc_to_fifo(chip->base, &opcode, 1);
+	aspeed_smc_to_fifo(chip->base, buf, len);
 	aspeed_smc_stop_user(nor);
 
 	return 0;
@@ -202,12 +296,12 @@ static void aspeed_smc_send_cmd_addr(struct spi_nor *nor, u8 cmd, u32 addr)
 		cmdaddr |= (u32)cmd << 24;
 
 		temp = cpu_to_be32(cmdaddr);
-		memcpy_toio(chip->base, &temp, 4);
+		aspeed_smc_to_fifo(chip->base, &temp, 4);
 		break;
 	case 4:
 		temp = cpu_to_be32(addr);
-		writeb(cmd, chip->base);
-		memcpy_toio(chip->base, &temp, 4);
+		aspeed_smc_to_fifo(chip->base, &cmd, 1);
+		aspeed_smc_to_fifo(chip->base, &temp, 4);
 		break;
 	}
 }
@@ -219,7 +313,7 @@ static int aspeed_smc_read_user(struct spi_nor *nor, loff_t from, size_t len,
 
 	aspeed_smc_start_user(nor);
 	aspeed_smc_send_cmd_addr(nor, nor->read_opcode, from);
-	memcpy_fromio(read_buf, chip->base, len);
+	aspeed_smc_from_fifo(read_buf, chip->base, len);
 	*retlen += len;
 	aspeed_smc_stop_user(nor);
 
@@ -233,7 +327,7 @@ static void aspeed_smc_write_user(struct spi_nor *nor, loff_t to, size_t len,
 
 	aspeed_smc_start_user(nor);
 	aspeed_smc_send_cmd_addr(nor, nor->program_opcode, to);
-	memcpy_toio(chip->base, write_buf, len);
+	aspeed_smc_to_fifo(chip->base, write_buf, len);
 	*retlen += len;
 	aspeed_smc_stop_user(nor);
 }
@@ -292,6 +386,14 @@ static int aspeed_smc_probe(struct platform_device *dev)
 	int err = 0;
 	unsigned int n;
 
+	/*
+	 * This driver passes ioremap addresses to io port accessors.
+	 * This works on arm if the IO_SPACE_LIMIT does not truncate
+	 * the address.
+	 */
+	if (~(unsigned long)IO_SPACE_LIMIT)
+		return -ENODEV;
+
 	match = of_match_device(aspeed_smc_matches, &dev->dev);
 	if (!match || !match->data)
 		return -ENODEV;
-- 
2.7.1